Bead-chain drive for roll up blinds

Abstract

The disclosed ball-chain drive for a wind-up blind has a chain-activated locking device that acts directly on the sprocket and remains effective even if the ball chain breaks or is jostled. The locking device in one form has such symmetry that the ball-chain drive is usable at either end of the wind-up blind.

What is claimed is: 
     
       1. A ball-chain drive for a roll-up blind that is weighted so that it tends to unroll, said drive including a support member, a sprocket carried by said support member and having regularly spaced peripheral pockets, a ball chain in mesh with the pockets of said sprocket, and a locking device selectively operable into position for locking said sprocket against rotation in at least one direction, said locking device having a dog selectively engageable with said sprocket for blocking rotation cf the sprocket and said locking device having an activating portion operable selectively by said ball chain into and out of position for causing the dog to engage with said sprocket. 
     
     
       2. A ball-chain drive as in claim 1 wherein said dog has a formation that cooperates with a pocket of the sprocket when the locking device locks the sprocket. 
     
     
       3. A ball-chain drive as in claim 1, wherein said ball chain when in cooperation with the activating portion of the locking device is arranged to shift said dog into cooperation with said sprocket when the sprocket draws the ball chain in said one direction. 
     
     
       4. A ball-chain drive as in claim 1, wherein said activating portion of the locking device includes at least one ball-receiving cavity and in which the dog has a formation receivable in a pocket of the sprocket, said formation being so spaced from said ball-receiving cavity of said activating portion that said formation tends to enter a ball-receiving cavity of said sprocket when the ball chain is meshed with the sprocket and a ball of the ball chain is received in said cavity. 
     
     
       5. A ball-chain drive as in claim 1, wherein said drive has obstructing means engageable by said locking device and wherein the locking device and the sprocket are so related that, after initial cooperation of the dog with the sprocket has been established by said activating portion, the sprocket in ensuing rotation carries the locking device against said obstructing means and thereby arrests the locking device which, in turn, arrests the sprocket against further rotation. 
     
     
       6. A ball-chain drive as in claim 1, wherein said locking device is a unitary part having an activating portion formed with at least one cavity for receiving a ball of the ball chain, a stop for arresting the locking device when the chain is pressed against said activating portion, said dog having a knob cooperable with a pocket of the sprocket, said knob being so spaced from said cavity in said activating portion that, when the ball chain is meshed with pockets of the sprocket and a ball of the ball chain is received in said cavity, rotation of the sprocket in said one direction causes the locking device to tilt about said stop and causes the knob to enter a pocket in the sprocket. 
     
     
       7. A ball-chain drive as in claim 6, wherein, when said knob is received in a said pocket, further rotation of the sprocket is effective to transport said locking device away from said stop, said ball-chain drive having means for blocking the transport of said locking device, thereby blocking the sprocket. 
     
     
       8. A ball-chain drive as in claim 1 for a wind-up blind that is weighted so that it tends to unwind, wherein said locking device has a second activating portion and a second dog cooperable with said sprocket, being mirror-images of the first-mentioned activating portion and the first-mentioned dog for adapting the ball-chain drive for use at either end of the wind-up blind. 
     
     
       9. A ball-chain drive as in claim 8, wherein each of said dogs is cooperable with a pocket of said sprocket. 
     
     
       10. A ball-chain drive as in claim 8, wherein said first-mentioned activating portion and said second activating portion and said first-mentioned dog and said second dog are portions of a unitary member. 
     
     
       11. A ball-chain drive for a wind-up blind that is weighted so that it tends to unwind, said drive including a support member, a sprocket carried by said support member and having regularly spaced peripheral pockets, a ball chain in mesh with an arcuate range of the pockets of said sprocket, a free range of the pockets remaining unoccupied by the ball chain, and a locking device selectively operable into position for locking said sprocket against rotation in at least one direction, said locking device having a dog cooperable with pockets of said sprocket in said free range and said locking device having an idle position in which the dog is disengaged from the sprocket, said locking device having an activating portion operable selectively by said ball chain for causing a portion of the dog to shift into a pocket of said sprocket. 
     
     
       12. A ball-chain drive as in claim 11 wherein incremental rotation of the sprocket displaces the dog while the dog remains in a pocket of the sprocket, and wherein the drive includes means for blocking the dog and thereby the sprocket against further rotation. 
     
     
       13. A ball-chain drive as in claim 11 wherein the chain is engageable with either of two opposite-end activating portions of the locking device and wherein the support member and the locking device have first cooperating portions that constrain the locking device to shift from its isle position into cooperation with the sprocket, the drive having means for maintaining that cooperation of the dog with the sprocket during an increment of rotation of the sprocket, and the drive having means for arresting the dog, thereby blocking further rotation of the sprocket. 
     
     
       14. A ball-chain drive for a wind-up blind, said drive including a support member, a rotary member carried by said support member and having regularly spaced peripheral pockets, a ball-chain in mesh with said pockets, and a locking device having a dog and said locking device being operable selectively by said ball chain for shifting the dog into interlocking engagement with the rotary member, and the drive having means for holding the dog of said locking device in interlocking engagement with the rotary member while the rotary member turns incrementally, the drive having means for arresting the locking device while the dog is held in interlocking engagement with the rotary member, the thus arrested locking device blocking the rotary member against further rotation. 
     
     
       15. A ball-chain drive as in claim 14, wherein said means for holding the dog in interlocked engagement with the rotary member includes mutually cooperative elements comprising a pin and an arcuate guide that curves around the rotary member, one of said cooperative elements being part of said support member and the other of said cooperative elements being part of said locking device, said arcuate guide having a relief for allowing disengagement of the dog from the rotary member for adapting the ball chain drive to be operated free of the locking device. 
     
     
       16. A ball-chain drive as in claim 15 wherein said arcuate guide is divided by said relief into two segments and wherein said locking device is operable by the ball chain for causing selective cooperation of said pin and either of said segments. 
     
     
       17. A drive for a wind-up blind wound on a core, there being a means tending to rotate the core in one direction for changing the amount of the blind that is wound on the core, said drive including a rotor to be unified to the core for rotation with the core, and a strand extending to said rotor and coupled to the rotor for operating the rotor in the direction opposite to said first direction, and   locking means for arresting said rotor at a desired wound-up adjustment of the blind, said locking means including an annular formation on the rotor comprising a series of indentations, and a locking member having a dog engageable with said annular formation in a non-slipping manner, said dog being disengaged from said annular formation while the rotor is being operated for adjusting the blind, said locking member being operable in an initial mode by said strand for engaging said dog with said annular formation and said locking member being operable in a further mode in which the dog remains in engagement with said annular formation while the rotor moves through an incremental rotation in said first direction, said locking means including means for arresting the locking member with the dog in non-slipping engagement with the annular formation and thereby terminating said incremental rotation.   
     
     
       18. A drive as in claim 17 wherein said strand is a ball chain and said indentations are pockets complementary to the ball chain for adapting the ball chain to drive said rotor.